Various systems have been proposed for checking the condition of storage racks of a machine which dispenses articles. The following U.S. patents are relevant to this subject matter.
U.S. Pat. No. 3,674,173 discloses a vending machine having microswitch pairs for sensing a sold-out condition of a pair of related dispensing columns.
U.S. Pat. No. 3,737,070 discloses a mechanical finger sensor to sense a sold-out condition of a particular shelf in a vending machine.
U.S. Pat. No. 3,838,663 discloses a light beam and shutter arrangement to detect blockages in dispensing chutes of a cigarette vending machine.
U.S. Pat. No. 4,057,171 discloses a vending machine having a microswitch to sense an absence of articles in a vending chute.
U.S. Pat. No. 4,075,463 discloses a hotel room vending unit which electronically records the consumption of goods and which is capable of transmitting this information to the hotel cashier's desk.
U.S. Pat. No. 4,267,942 discloses a dispensing unit with an electronic recording system capable of automatically accounting for items dispensed, date and time of removal, and identification of the recipient using an assigned key.
U.S. Pat. No. 4,350,238 discloses a data acquisition unit utilizing a microcomputer in a vending machine to record, through connection with various selection switches, the number of vends of each product and price data. It is capable of driving a printout device to display such data and simultaneously retaining such data in its memory.
The sensing of the condition of a dispensing or vending machine has heretofore been a very complex procedure, as shown by the aforementioned patents.